The present invention relates to an electron-emitting device manufacturing method and apparatus, electron-emitting device driving method, and electron-emitting device adjusting method.
Conventionally, electron-emitting devices are mainly classified into two types of devices: thermionic and cold cathode electron-emitting devices. Known examples of the cold cathode electron-emitting devices are field emission type electron-emitting devices (to be referred to as FE type electron-emitting devices hereinafter), metal/insulator/metal type electron-emitting devices (to be referred to as MIM type electron-emitting devices hereinafter), and surface-conduction emission type electron-emitting devices. Known examples of the FE type electron-emitting devices are disclosed in W. P. Dyke and W. W. Dolan, xe2x80x9cField emissionxe2x80x9d, Advance in Electron Physics, 8, 89 (1956) and C. A. Spindt, xe2x80x9cPHYSICAL Properties of thin-film field emission cathodes with molybdenium conesxe2x80x9d, J. Appl. Phys., 47, 5248 (1976). A known example of the MIM type electron-emitting devices is disclosed in C. A. Mead, xe2x80x9cOperation of Tunnel-Emission Devicesxe2x80x9d, J. Appl. Phys., 32,646 (1961). A known example of the surface-conduction emission type electron-emitting devices is disclosed in, e.g., M. I. Elinson, Radio Eng. Electron Phys., 10, 1290 (1965).
The surface-conduction emission type device utilizes the phenomenon that electrons are emitted from a small-area thin film formed on a substrate by flowing a current parallel through the film surface. The surface-conduction emission type electron-emitting device includes electron-emitting devices using an SnO2 thin film according to Elinson mentioned above [M. I. Elinson, Radio Eng. Electron Phys., 10, 1290, (1965)], an Au thin film [G. Dittmer, xe2x80x9cThin Solid Filmsxe2x80x9d, 9,317 (1972)], an In2O3/SnO2 thin film [M. Hartwell and C. G. Fonstad, xe2x80x9cIEEE Trans. ED Conf.xe2x80x9d, 519 (1975)], a carbon thin film [Hisashi Araki et al., xe2x80x9cVacuumxe2x80x9d, Vol. 26, No. 1, p. 22 (1983)], and the like.
The FE, MIM, and surface-conduction emission type electron-emitting devices have an advantage that many devices can be arranged on a substrate. Various image display apparatuses using these devices have been proposed.
The surface-conduction emission type electron-emitting device emits electrons from an electron-emitting portion formed in a conductive thin film by flowing a current parallel to the surface of the small-area conductive thin film formed on a substrate. Since this device has a simple structure and can be easily manufactured, many devices can be formed on a wide area, and applications to, e.g., image display apparatuses and the like have been studied. Applications of a surface-conduction emission type electron-emitting device to an image display apparatus are disclosed in U.S. Pat. No. 5,066,883 and Japanese Patent Laid-Open No. 6-342636 filed by the assignee of the present applicant. These references disclose image forming means and manufacturing methods. In an image forming means, a plurality of surface-conduction emission type electron-emitting devices are two-dimensionally arranged each of which has a pair of device electrodes formed on a substrate, a conductive film connected to the pair of device electrodes, and an electron-emitting portion formed in the conductive film. An electrical selection means is adopted to individually select electrons emitted from each electron-emitting device. An image is formed in accordance with an input signal. Japanese Patent Laid-Open No. 7-235255 filed by the assignee of the present applicant discloses the following technique. A voltage is applied to a surface-conduction emission type electron-emitting device in an organic atmosphere to deposit a deposit mainly containing carbon near an electron-emitting portion in order to improve the electron-emitting characteristics of the surface-conduction emission type electron-emitting device. According to the technique of Japanese Patent Laid-Open No. 7-235275 filed by the assignee of the present applicant, electron-emitting characteristics are stabilized by a means of setting the residual partial pressure of an organic substance to 1.3xc3x9710xe2x88x926 Pa or less in an environment where an electron-emitting device is formed. According to the technique of Japanese Patent Laid-Open No. 9-259753 filed by the assignee of the present applicant, a voltage pulse higher than the sum of the maximum value of a normal driving voltage and a noise voltage which may be applied to a surface-conduction emission type electron-emitting device is applied to a plurality of surface-conduction emission type electron-emitting devices arranged two-dimensionally in an atmosphere in which the partial pressure of an organic gas is 1.3xc3x9710xe2x88x926 Pa or less. This suppresses irreversible unstableness of an emission current caused by the temperature characteristics or disturbance of a driving circuit in normal driving, and reduces luminance irregularity.
An image display apparatus using such surface-conduction emission type electron-emitting device formed by the above method is expected to exhibit more excellent characteristics than other types of conventional image display apparatuses. For example, this image display apparatus is superior to recent popular liquid crystal display apparatuses in that it does not require a backlight because of a self-emission type and has a wide view angle.
As described above, the surface-conduction emission type electron-emitting device has a simple structure, can be easily manufactured, and exhibits excellent electron-emitting characteristics. For this reason, the electron-emitting device is suitable for constituting an image forming apparatus, such as a large-size self-emission flat display using a fluorescent substance as an image forming member. Applications to various analyzers and processors using electron sources are also expected. Considering applications to image forming apparatuses and the like, the electron-emitting device is required to stably keep emitting an expected electron beam amount. To provide image forming apparatuses and analyzers with high reliability, conventional electron-emitting devices must attain more stable electron-emitting characteristics.
It is an object of the present invention to provide a manufacturing method capable of manufacturing a preferable electron-emitting device, a manufacturing apparatus for a preferable electron-emitting device, a driving method for a preferable electron-emitting device, and an adjusting method for a preferable electron-emitting device.
It is another object of the present invention to realize stable electron-emitting characteristics in an electron-emitting device.
To achieve the above objects, an electron-emitting device manufacturing method according to the present invention has the following step.
That is, a method of manufacturing an electron-emitting device which has at least two electrodes and emits electrons by applying a voltage between the two electrodes is characterized by comprising:
the voltage application step of applying a voltage between the two electrodes constituting the electron-emitting device, the voltage application step including applying a voltage of the same polarity (to be also referred to as a positive polarity hereinafter) as a polarity of a voltage applied in normal driving, and applying a voltage of an opposite polarity to the polarity of the voltage applied in normal driving.
The magnitude of the voltage of the same polarity is preferably larger than the magnitude of the voltage applied in normal driving. The magnitude of the voltage of the opposite polarity is preferably larger than the magnitude of the voltage applied in normal driving. The magnitude of the voltage of the opposite polarity is preferably smaller than the magnitude of the voltage of the same polarity.
The voltage application step is preferably performed in a high-vacuum atmosphere. When the two electrodes have a gap therebetween, the voltage application step is preferably performed in an atmosphere in which the gap between the two electrodes is not made narrow by deposition of a substance in the atmosphere or a substance originating from the substance in the atmosphere in the voltage application step. The voltage application step is preferably performed in an atmosphere in which carbon and a carbon compound in the atmosphere have a partial pressure of not more than 1xc3x9710xe2x88x926 Pa. The voltage application step is preferably performed in substantially the same atmosphere as in normal driving.
The present invention can be most preferably adopted when the electron-emitting device manufacturing method further comprises the step of forming the two electrodes having a gap therebetween prior to the voltage application step.
The electron-emitting device manufacturing method according to the present invention can be preferably employed as a cold cathode device manufacturing method. Especially, the method of the present invention can be preferably employed as a method of manufacturing a field emission type electron-emitting device, a surface-conduction emission type electron-emitting device, or an MIM type electron-emitting device having an insulating layer between two electrodes. More particularly, the method of the present invention can be preferably employed as a method of manufacturing an electron-emitting device having a gap between two electrodes. For example, in a Spindt field emission type electron-emitting device, an emitter cone electrode and gate electrode serve as two electrodes having a gap therebetween. In a surface-conduction emission type electron-emitting device, a high-potential electrode and low-potential electrode serve as two electrodes having a gap therebetween. In the surface-conduction emission type electron-emitting device having a pair of device electrodes and a conductive film between them, the gap of the conductive film serves as the above-described gap.
For example, the surface-conduction emission type electron-emitting device is known to use a technique of executing in the manufacture a step called an activation step of depositing carbon or a carbon compound in a gap between two electrodes. This activation can form two electrodes having a gap therebetween in which a deposit is deposited. The present invention can be especially preferably applied to this structure in which the deposit is deposited in the gap between the electrodes. When depositing the deposit uses the deposition step of depositing a substance in the atmosphere or a substance originating from the substance in the atmosphere, the voltage application step of the present invention is desirably performed after the partial pressure of the substance serving as a deposit is decreased upon the deposition step.
In the present invention, the voltage application step preferably comprises applying a pulse voltage. The present invention preferably adopts the step of applying the pulse voltage a plurality of number of times.
In the present invention, the voltage application step preferably comprises alternately applying pulses of the voltage of the same polarity and pulses of the voltage of the opposite polarity. The present invention preferably adopts the step of repeating alternate voltage application a plurality of number of times.
In the present invention, a total application time of the voltage of the positive polarity in the voltage application step is preferably not less than 500 xcexcsec, and/or not more than 60 sec. A total application time of the voltage of the opposite polarity in the voltage application step is not more than a total application time of the voltage of the positive polarity. In this case, the total voltage application time is a total application time of pulses in application of a pulse voltage.
The present invention includes a manufacturing apparatus used in the electron-emitting device manufacturing method, and the manufacturing apparatus comprises a potential output portion for applying a voltage between the two electrodes. As the potential output portion, a power source 51 shown in FIG. 6 can be used.
The present invention incorporates an electron-emitting device driving method. That is, a method of driving an electron-emitting device which has at least two electrodes and emits electrons by applying a voltage between the two electrodes is characterized in that
the electron-emitting device is manufactured or adjusted through the voltage application step of applying voltages of opposite polarities between the two electrodes constituting the electron-emitting device,
wherein, in driving, a voltage of one polarity among the voltages of opposite polarities is applied between the two electrodes to perform normal driving.
The present invention incorporates an electron-emitting device adjusting method having the following step.
That is, a method of adjusting an electron-emitting device which has at least two electrodes and emits electrons by applying a voltage between the two electrodes is characterized by comprising:
the voltage application step of applying a voltage between the two electrodes constituting the electron-emitting device, the voltage application step including applying a voltage of the same polarity as a polarity of a voltage applied in normal driving, and applying a voltage of an opposite polarity to the polarity of the voltage applied in normal driving.
This adjusting method can be preferably used when a manufactured electron-emitting device is adjusted after shipping.
These driving and adjusting methods can also adopt the same conditions as described for the manufacturing method.
The present invention provides an electron-emitting device whose emission current is stable for a long time, as will be described later. By applying the present invention to the manufacture or adjustment of an image forming apparatus or the like, an image forming apparatus with high reliability can be provided.